Nurse Niels Högel goes on trial in Germany over 100 patient deaths

Hoegel was convicted in 2015 of two murders and two attempted murders at a hospital in the town of Delmenhorst. German laws also does not allow for consecutive prison terms, so Hoegel could theoretically walk free within little more than a decade, unless he is barred from an early release at the end of the trial that is now underway.

Hoegel was caught red-handed injecting unauthorized drugs into a patient in 2005 but no one at the hospital intervened.

"We fought for four years for this trial and expect Hoegel is sentenced for another 100 murders", said Marbach, whose grandfather was killed by Hoegel, the BBC reported.

A commemorative plaque for victims of the nurse Niels Hoegel.

Psychiatrists who have evaluated Hoegel, the father of an adolescent daughter, say he has a severe narcissistic disorder.

Prosecutors say he was motivated by vanity, to show off his skills at saving human lives, and by simple "boredom".

Hoegel himself said he craved "the positive feedback" he got for saving a life and used painkillers to deal with "the stress" of the job.

The serial killer owned up to his crimes today in the north-western city of Oldenburg.

In prior hearings, Hoegel is reportedly said to have been seeking a sense of euphoria after having resuscitated a patient from an emergency situation he himself created.

The hospital in Oldenburg dismissed Hoegel in late 2002 due to mounting suspicions about the deaths of patients on his watch.

After a minute of silence for the victims, the bearded, heavyset Hoegel listened impassively, his head lowered, as prosecutor Daniela Schiereck-Bohlmann read out the name of each dead patient and the charges against the defendant.

The figures paint a damning picture but prosecutors only took action in 2008, ordering the exhumation of eight bodies under pressure from relatives of alleged victims.